This invention relates generally to the structure of footwear. More specifically, this invention relates to the structure of athletic shoe soles that copy the underlying support, stability and cushioning structures of the human foot. Still more particularly, this invention relates to the use of relatively inelastic and flexible fiber within the material of the shoe sole to provide both flexibility and firmness under load-bearing pressure. It also relates to the use of sipes, particularly those that roughly parallel the foot sole of the wearer in frontal plane cross sections, contained within the shoe sole under the load-bearing structures of the wearer's foot to provide the firmness and flexibility to deform to flatten under weight-bearing loads in parallel with the wearer's foot sole. Finally, it relates to providing additional shoe sole width to support those areas identified as mandatory to maintaining the naturally firm lateral and medial support of the wearer's foot sole during extreme sideways motion while load-bearing.
This application is built upon the applicant's earlier U.S. applications, especially including Ser. No. 07/463,302, filed Jan. 10, 1990. That earlier application showed that natural stability is provided by attaching a completely flexible but relatively inelastic shoe sole upper directly to the bottom sole, enveloping the sides of the midsole, instead of attaching it to the top surface of the shoe sole. Doing so puts the flexible side of the shoe upper under tension in reaction to destabilizing sideways forces on the shoe causing it to tilt. That tension force is balanced and in equilibrium because the bottom sole is firmly anchored by body weight, so the destabilizing sideways motion is neutralized by the tension in the flexible sides of the shoe upper. Still more particularly, this invention relates to support and cushioning which is provided by shoe sole compartments filled with a pressure-transmitting medium like liquid, gas, or gel. Unlike similar existing systems, direct physical contact occurs between the upper surface and the lower surface of the compartments, providing firm, stable support. Cushioning is provided by the transmitting medium progressively causing tension in the flexible and relatively inelastic sides of the shoe sole. The compartments providing support and cushioning are similar in structure to the fat pads of the foot, which simultaneously provide both firm support and progressive cushioning.
Existing cushioning systems cannot provide both firm support and progressive cushioning without also obstructing the natural pronation and supination motion of the foot, because the overall conception on which they are based is inherently flawed. The two most commercially successful proprietary systems are Nike Air, based on U.S. Pat. Nos. 4,219,945 issued Sep. 2, 1980, 4,183,156 issued Sep. 15, 1980, 4,271,606 issued Jun. 9, 1981, and 4,340,626 issued Jul. 20, 1982; and Asics Gel, based on U.S. Pat. No. 4,768,295 issued Sep. 6, 1988. Both of these cushioning systems and all of the other less popular ones have two essential flaws.
First, all such systems suspend the upper surface of the shoe sole directly under the important structural elements of the foot, particularly the critical the heel bone, known as the calcaneus, in order to cushion it. That is, to provide good cushioning and energy return, all such systems support the foot's bone structures in buoyant manner, as if floating on a water bed or bouncing on a trampoline. None provide firm, direct structural support to those foot support structures; the shoe sole surface above the cushioning system never comes in contact with the lower shoe sole surface under routine loads, like normal weight-bearing. In existing cushioning systems, firm structural support directly under the calcaneus and progressive cushioning are mutually incompatible. In marked contrast, it is obvious with the simplest tests that the barefoot is provided by very firm direct structural support by the fat pads underneath the bones contacting the sole, while at the same time it is effectively cushioned, though this property is underdeveloped in habitually shoe shod feet.
Second, because such existing proprietary cushioning systems do not provide adequate control of foot motion or stability, they are generally augmented with rigid structures on the sides of the shoe uppers and the shoe soles, like heel counters and motion control devices, in order to provide control and stability. Unfortunately, these rigid structures seriously obstruct natural pronation and supination motion and actually increase lateral instability, as noted in the applicant's U.S. application Ser. Nos. 07/219,387, filed on Jul. 15, 1988; 07/239,667, filed on Sep. 2, 1988; 07/400,714, filed on Aug. 30, 1989; 07/416,478, filed on Oct. 3, 1989; 07/424,509, filed on Oct. 20, 1989; 07/463,302, filed on Jan. 10, 1990; 07/469,313, filed on Jan. 24, 1990; 07/478,579, filed Feb. 8, 1990; 07/539,870, filed Jun. 18, 1990; 07/608,748, filed Nov. 5, 1990; 07/680,134, filed Apr. 3, 1991; 07/686,598, filed Apr. 17, 1991; and 07/783,145, filed Oct. 28, 1991, as well as in PCT and foreign national applications based on the preceding applications. The purpose of the inventions disclosed in these applications was primarily to provide a neutral design that allows for natural foot and ankle biomechanics as close as possible to that between the foot and the ground, and to avoid the serious interference with natural foot and ankle biomechanics inherent in existing shoes.
In marked contrast to the rigid-sided proprietary designs discussed above, the barefoot provides stability at it sides by putting those sides, which are flexible and relatively inelastic, under extreme tension caused by the pressure of the compressed fat pads; they thereby become temporarily rigid when outside forces make that rigidity appropriate, producing none of the destabilizing lever arm torque problems of the permanently rigid sides of existing designs.
The applicant's new invention simply attempts, as closely as possible, to replicate the naturally effective structures of the foot that provide stability, support, and cushioning. This application is also built on the applicant's earlier U.S. application Ser. No. 07/539,870, filed Jun. 18, 1990. That earlier application related to the use of deformation sipes such as slits or channels in the shoe sole to provide it with sufficient flexibility to parallel the frontal plane deformation of the foot sole, which creates a stable base that is wide and flat even when tilted sideways in natural pronation and supination motion.
The applicant has introduced into the art the use of sipes to provide natural deformation paralleling the human foot in U.S. application Ser. Nos. 07/424,509, filed Oct. 20, 1989, and 07/478,579, filed Feb. 8, 1990. It is the object of this invention to elaborate upon those earlier applications to apply their general principles to other shoe sole structures, including those introduced in other earlier applications.
By way of introduction, the prior two applications elaborated almost exclusively on the use of sipes such as slits or channels that are preferably about perpendicular to the horizontal plane and about parallel to the sagittal plane, which coincides roughly with the long axis of the shoe; in addition, the sipes originated generally from the bottom of the shoe sole. The '870 application elaborated on use of sipes that instead originate generally from either or both sides of the shoe sole and are preferably about perpendicular to the sagittal plane and about parallel to the horizontal plane; that approach was introduced in the '509 application. The '870 application focused on sipes originating generally from either or both sides of the shoe sole, rather than from the bottom or top (or both) of the shoe sole, or contained entirely within the shoe sole.
The applicant's prior application on the sipe invention and the elaborations in this application are modifications of the inventions disclosed and claimed in the earlier applications and develop the application of the concept of the theoretically ideal stability plane to other shoe structures. Accordingly, it is a general object of the new invention to elaborate upon the application of the principle of the theoretically ideal stability plane to other shoe structures.
Accordingly, it is a general object of this invention to elaborate upon the application of the principle of the natural basis for the support, stability and cushioning of the barefoot to shoe structures.
It is still another object of this invention to provide a footwear using relatively inelastic and flexible fiber within the material of the shoe sole to provide both flexibility and firmness under load-bearing pressure.
It is still another object of this invention to provide footwear that uses sipes, particularly those that roughly parallel the foot sole of the wearer in frontal plane cross sections, contained within the shoe sole under load-bearing foot structures to provide the firmness and flexibility to deform to flatten under weight-bearing loads in parallel with the wearer's foot sole.
It is another object of this invention to provide additional shoe sole width to support those areas identified as most critical to maintaining the naturally firm lateral and medial support of the wearer's foot sole during extreme sideways motion while load-bearing.
These and other objects of the invention will become apparent from a detailed description of the invention which follows taken with the accompanying drawings.